Apparatus and method for controlling the end of fill of a fluid actuated clutch

ABSTRACT

The present invention discloses a system and a method for controlling the timing of the filling of a fluid actuate. The system includes, a fluid actuated clutch  83,  an electronic controller adapted to detect an end-of-fill point for the fluid actuated clutch  83,  compare the end-of-fill point with a desired end-of-fill point and adjust at least one of a plurality of clutch fill parameters in response to the comparison in order to control the timing of the filling of the clutch  83,  and a control valve that is activated by the electronic controller.

TECHNICAL FIELD

This invention relates generally to a method of clutch control and, moreparticularly, to a method of controlling the end-of-fill point for afluid actuated clutch.

BACKGROUND ART

In general, the output shaft of an engine is typically connected to aninput shaft of a torque converter and an output shaft of a torqueconverter is typically connected to an input shaft of a transmission.The lock-up clutch is located between the input shaft and output shaftof a torque converter so as to provide a rotatable connection. Anelectronic control system is typically utilized to smoothly engage anddisengage a fluid actuated clutch. The clutch is interfaced to anassociated solenoid valve through the electronic control system. Thesolenoid valve is modulated to control the clutch pressure in responseto command signals from the electronic control system.

To precisely time the engagement of the clutch, the fill time is animportant parameter. Fill time is defined as the time required to fillan oncoming clutch cavity with fluid. During this fill period, a clutchpiston will stroke and clutch plates will move to the point of“touch-up”. However, until the clutch plates are compressed together,the clutch cannot transmit any significant torque. Therefore, theend-of-fill time is important to ascertain when this critical moment isreached. A harsh engagement can result in a torque spike that istransmitted through the drivetrain of the machine and creates a “jerk”.This jerk is uncomfortable to the operator and diminishes the lifeexpectancy of the associated drivetrain components of the machine.

One known arrangement utilizes a separate flow sensing valve having anelectrical switch disposed thereon. The flow into the flow sensing valveis directed through a fixed orifice to the associated hydraulic clutch.Once the flow through the valve ceases, the absence of a pressure dropacross the fixed orifice permits the flow sensing valve to return to aspring biased, flow blocking position. Once the flow sensing valve is inthe spring biased position, this triggers an electrical switch thatindicates that the clutch is filled. A major drawback with thisarrangement is that it requires all fluid to flow through a fixedorifice and also through a separate flow sensing switch for each clutchin the system.

Still another known mechanism for determining end-of-fill is to controlthe amount of time that fluid is allowed to flow toward the clutch.These arrangements do not account for variances in control valves orclutch activating chambers. To overcome these variances, a number ofcontrol schemes have been devised to adaptively change the fill timebased on previous clutch fills. However, these control schemes depend oncostly and time consuming calibration techniques.

Yet another technique for determining the end-of-fill point involvesmonitoring the electronic activation of the control valve that directsfluid to the clutch. When the actuating chamber of the clutch is full,the increase in pressure operates upon the control valve to move it backto a flow blocking position. The force that is acting to move thecontrol valve back to the flow blocking position is acting against theelectrical force that moved the control valve to the flow passingposition. This creates an electrical voltage spike that is detected byan electronic controller. This voltage spike represents the end-of-fillpoint.

The present invention is directed to overcoming one or more of theproblems set forth above.

DISCLOSURE OF THE INVENTION

In one aspect of this invention, a system for controlling the timing ofthe filling of a fluid actuated clutch is disclosed. The systemcomprises a fluid actuated clutch, an electronic controller adapted todetect an end-of-fill point for the fluid actuated clutch, and comparethe end-of-fill point with a desired end-of-fill point and a controlvalve that is activated by the electronic controller. The control valveis operatively connected to the fluid actuated clutch.

In another aspect of the present invention, a method for controlling thetiming of the filling of a fluid actuated clutch is disclosed. Theclutch is operatively connected to a control valve that is activated byan electronic controller. The method includes the steps of determiningan end-of-fill point, comparing said end-of-fill point with a desiredend-of-fill point, and responsively controlling the timing of thefilling of the fluid actuated clutch.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference may bemade to the accompanying drawings in which:

FIG. 1 is a block diagram of an electronic control system of a machineincluding an engine, drivetrain, transmission, torque converter and afluid actuated clutch;

FIG. 2 is a block diagram illustrating an embodiment of a hydraulicsystem for a fluid actuated clutch;

FIG. 3 is a timing chart illustrating the current level during the pulsetime, ramp time, hold time, modulation time, and end-of-fill point incorrelation with instantaneous clutch slip;

FIG. 4 is a flowchart illustrating software for determining theend-of-fill point for a fluid actuated clutch;

FIG. 5 is a timing chart illustrating the current level during the pulsetime, ramp time, hold time, modulation time, and end-of-fill point incorrelation with a desired end-of-fill region;

FIG. 6 illustrates one example of a modified command pulse sequence;

FIG. 7 illustrates a second example of a modified command pulsesequence; and

FIG. 8 is a flow chart illustrating software for controlling the timingof the filling of the clutch.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, and initially to FIG. 1, an electroniccontrol system 8 of a power train 10 is depicted that includes aninternal combustion engine 12, a fluidic torque converter 14, amulti-speed fluid operated power transmission 16, and a machinedrivetrain 18. The engine 12 is connected to the torque converter 14 bya first shaft 20, the torque converter 14 is connected to thetransmission 16 by a second shaft 22, and the transmission 16 isconnected to the machine drivetrain 18 by a third shaft 24. The shafts20, 22, and 24 can be eliminated with the combustion engine 12, thefluidic torque converter 14, and the multi-speed fluid operated powertransmission 16 being directly connected together. This type ofinterconnection would depend on the type of machine. The torqueconverter 14 includes an impeller 45 coupled to the first shaft 20, aturbine member 46 coupled to the second shaft 22, and a stator member 48that may be grounded to a housing 49 for the torque converter 14.

The control portion of the drivetrain will now be discussed. An operatorproduces a desired engagement of a fluid actuated clutch 83 through theactivation of a clutch enable switch 81. The clutch enable switch 81 isoptional and not always necessary for activation of the fluid actuatedclutch 83. An electronic control module 40 receives the clutch enablesignal and then controls the operation of a solenoid control valve 77.The electronic control system also receives various other inputsrepresenting machine system parameters. These other inputs include anengine speed signal from an engine speed sensor 42 and a torqueconverter output signal from a torque converter output sensor 44. Theclutch slip is defined as the difference between the input speed and theoutput speed of the clutch. For a lock-up clutch it is defined as thedifference between the engine speed and the torque converter outputspeed.

The engine speed sensor 42 and the torque converter output sensor 44 arepreferably conventional electrical transducers. A typical, butnonlimiting example of a conventional electrical transducer would be amagnetic speed pickup. However, numerous other types and methods ofspeed sensing may be utilized.

The electronic control module 40 delivers a clutch command signal thatis proportional to the desired current needed to operate the solenoidcontrol valve 77. In the preferred embodiment, the current driverutilizes a pulse width modulated voltage to produce the desired current.The solenoid control valve 77 is configured to maintain communication ofoil to a proportional control valve 28, that is sufficient to maintain aclutch pressure that is proportional to the solenoid current once theclutch 83 is filled. Therefore, the electronic control module 40controls the clutch pressure by means of a proportional command signalprovided to the solenoid control valve 77 that operates the clutch 83.In the preferred embodiment, the command signal is in the form of acurrent based signal. An increased current energizes the solenoidcontrol valve 77, thereby operating the clutch 83.

Referring now to FIG. 2, a block diagram of a hydraulic system for theclutch 83 is shown. As merely an illustrative example, FIG. 2 representsa lock-up clutch that is sometimes referred to as a slipping clutch. Thepurpose of the lock-up clutch is to provide better machine performanceduring a load or carry operation. The lock-up-clutch will engage whenthe torque converter output speed is over a predetermined speed and willdisengage when the torque converter output speed is below thispredetermined torque converter output speed. When the lock-up clutch isengaged, the torque converter will be bypassed. This will provide adirect connection between the engine and the transmission. The clutch 83is actuated by hydraulic pressure and upon engagement, requires arequisite amount of fill time before torque is initiated between afriction element that provides a driving force and a friction elementthat is driven by the friction element having the driving force. Inother words, the fill time is the elapsed time between the time that theclutch piston moves from the released to the initial engagementposition. The clutch 83 is selectively engaged and disengaged by meansof the proportional pressure control valve 28.

The hydraulic circuit of the transmission includes a positivedisplacement pump 30 that supplies pressurized hydraulic fluid from thesump or reservoir 32, through a filtering unit 34, to the clutch 83through the control valve 28. Optionally, a pressure relief valve 36 maybe added to regulate the valve supply pressure. When the clutch 83disengages, excess hydraulic fluid returns to the sump or reservoir 32.Although a lock-up clutch has been mentioned, the present inventioncould be directed to torque transmitting types of clutches that are notdefined as a type of lock-up clutch.

The command pulses utilized to perform a fluid actuated clutch shift aredepicted in FIG. 3. Immediately at the start of the clutch shift, thereis a small pulse delay time period. The command pulse is pulsed at arelatively high level for a predetermined period of time. This commandpulse to the solenoid valve 77 quickly opens the control valve 28 tobegin filling the fluid actuated clutch 83 and thereby stroking therespective fluid actuated clutch piston. The fluid actuated clutchcommand is then decreased from a ramp level during the ramp time to ahold level having a duration sufficient to completely fill the fluidactuated clutch 83. The value of the hold level is high enough to ensurecompletion of clutch fill and yet low enough to prevent torque spikewhen the clutch plates “touch up”. After the fluid actuated clutch 83 isfilled, the clutch pressure enters a modulation time period. Thismodulation phase can utilize either an open or closed loop control togradually increase the clutch pressure to cause a desired decrease inclutch slip. The pressure within the clutch 83 is increased to and heldat a level sufficient to maintain the clutch 83 in its fully engagedposition.

Once the end-of-fill point is detected, a smooth transition into themodulation time period may result so that the clutch pressure is slowlyand gradually increased with a corresponding decrease in clutch slip.This will prevent the torque spike that causes jerk and createsdiscomfort to the operator as well as decreasing the life expectancy ofthe drivetrain components. Either early or late engagement will cause atorque spike. The end-of-fill point should occur during the hold timewhen pressure on the clutch 83 is the lowest.

Also, as shown in FIG. 3, the instantaneous clutch slip is depicted incorrelation with the current level of the fill parameters. In thepreferred embodiment, the end-of-fill may be identified as the point intime when the instantaneous value of the clutch slip is less than areference value of the clutch slip. The reference value of the clutchslip is dynamically determined during the operation of the clutch. Inthe preferred embodiment, the reference value of the clutch slip isdynamically determined based on an average of a predetermined number ofloops or cycles of instantaneous clutch slip that is divided by apredetermined factor. Even a single cycle might suffice. The preferredpredetermined factor represents a fixed percentage of the average clutchslip. This percentage typically ranges between thirty percent (30%) andfifty percent (50%) with the optimal value being thirty percent (30%).In an alternative embodiment, the reference value is dynamicallydetermined by using a low pass digital filter software algorithm tofilter the instantaneous clutch slip value, the output of the filterbeing divided by the predetermined factor. As illustrated, a firstinstantaneous clutch slip level 50 presents a marked contrast to asecond clutch slip level 52. The instantaneous clutch slip level at 52will be less than the reference clutch slip value so that at this point,the clutch slip indicates the end-of-fill for that clutch. The referenceclutch slip value is preferably computed prior to the initiation of thecommand pulse. However, computation of the reference clutch slip valuecan occur at any time while the clutch slip is at the firstinstantaneous clutch slip level 50.

As shown, once the clutch 83 reaches the point of “touch-up”, theinstantaneous clutch slip will remain at this lower level, however,these later clutch slip values are not relevant because the end-of-fillpoint has already been determined. This predetermined factor variesdepending on the design and structure of the respective clutch 83, thetype and nature of the machine, the machine manufacturer, the number ofcycles, and any software scaling factors. An illustrative, butnonlimiting, example would include a predetermined factor representingthirty (30%) of the average clutch slip or in the alternative, apredetermined factor of three (3) and a predetermined number of cyclesor loops as ten (10) could be used for some motor graders, wheel loadersand off-highway trucks.

The preferred embodiment of the end-of-fill detecting software will nowbe discussed with reference to FIG. 4, which depicts a flowchartrepresentative of the computer program instructions executed by theelectronic control module 40 shown in FIG. 1. A programmer skilled inthe art could utilize this flowchart to program any of a wide variety ofelectronic controllers/computers in a wide variety of programminglanguages. In the description of the flowcharts, the functionalexplanation marked with numerals in angle brackets, <nnn>, will refer tothe flowchart blocks bearing that number. As shown in FIG. 4, theprogram first determines whether a clutch command is present <60>. Ifthe answer is no, the counter will be set to zero <74> and the processwill stop. If the answer is yes, then a counter will be incremented byone (1) <62>. Preferably, the value of the counter is correlated to avalue in real time by a timing function associated with the electroniccontrol module 40.

There are four steps, although not critical to the process in principle,which attempt to minimize the possibility of detecting a falseend-of-fill point and operate as a safeguard. These four steps arepreferably monitored throughout the process or may be monitored onceprior to the start of a primary program step.

The first of these steps involves the determination of whether theselected gear is present <64>. This selected gear is totally dependenton the type of engine utilized in a particular machine. An illustrative,but nonlimiting example, is equal or greater than second gear and lessthan or equal to third gear for motor graders, wheel loaders, andoff-highway trucks. If the answer to this query is no, the counter isset to zero <74> and the program stops. Otherwise, the program willprogress to the next step.

The second safeguard step is a determination of whether the engine speedexceeds a minimum threshold value <66>. Once again, these limits aredependent on the parameters of the clutch and a failure to be above thisminimum threshold will result in the counter being set to zero <74>. Anillustrative, but nonlimiting example, is an engine speed of 1,500revolutions per minute for motor graders, wheel loaders, and off-highwaytrucks.

The third safeguard step is a determination of whether the torqueconverter slip is monotonically decreasing by a predetermined value overa predetermined number of cycles <67>. Once again, these limits aredependent on the parameters of the clutch and a failure to decrease overa predetermined number of cycles will result in the counter being set tozero <74>. An illustrative, but nonlimiting example, is a decrease overtwo or more cycles or loops for motor graders, wheel loaders, andoff-highway trucks.

The fourth safeguard step merely compares the value of the counter witha predetermined time interval. A nonlimiting example of this timeinterval would include a summation of the pulse, ramp, hold, andmodulation times <68>. If the value of the counter exceeds the summationof these time periods, the counter will be set to zero <74> and theprogram will stop. This is because the point in time representing theend of the fill period will have past.

The primary program step makes the determination as to whether or notthe instantaneous clutch slip is less than a reference clutch slip value<68>. As previously described above, this predetermined factor and thenumber of loops or cycles vary depending on the design and structure ofthe clutch. The design and structure of the clutch depends upon the typeand nature of the machine as well as the machine manufacturer. Inaddition, the parameters may be altered due to different scaling factorsin the software. An illustrative, but nonlimiting, example would includea predetermined factor of three (3) and the number of loops or cyclesbeing ten (10) for motor graders, wheel loaders, and off-highway trucks.

The software will keep looping through this primary program step <70>,the step of incrementing the counter by one (1) <62>, the firstsafeguard step <64>, the second safeguard step <66>, the third safeguardstep <67> and the fourth safeguard step <68>, until this condition isreached and will then save the counter value at this point as theend-of-fill point <72>.

Once the end-of-fill point has been detected, the present inventionprovides a method for controlling the timing of the filling of the fluidactuated clutch 83. The method includes the steps of comparing theend-of-fill point with a desired end-of-fill point, and then dynamicallyadjusting at least one of a plurality of clutch fill parameters inresponse to the comparison. In the preferred embodiment, the desiredend-of-fill point is a region, and the clutch fill parameter(s) areadjusted when the comparison indicates the end-of-fill point occurredoutside the desired region.

The dynamic adjustment of the timing of the end-of-fill point will nowbe discussed. FIG. 5 illustrates one embodiment of the clutch commandpulses delivered to the solenoid control valve 83 by the electroniccontrol module 40. As illustrated, the parameters of the clutch fillcommands include a current level, or value, and a time duration. Inaddition, the duration over which a clutch 83 is filled may becharacterized as including a pulse delay time, pulse time, fill ramptime, hold time, and modulation ramp time. Each time duration may beassociated with a clutch fill command, e.g., a hold command or a fillramp command. In the preferred embodiment, as stated above, theend-of-fill point occurs during the hold time enabling a smoothtransition into the modulation time period, illustrated in 3. The smoothtransition will prevent the torque spike that causes jerk and createsdiscomfort to the operator as well as decreasing the life expectancy ofthe drivetrain components.

In one embodiment, the hold time may be further characterized as apre-desired end-of-fill hold time, desired end-of-fill region, andpost-desired-end-of-fill hold time, as illustrated in FIG. 5. Theend-of-fill point may be adjusted, by controlling the amount and ratethe fluid fills the clutch 83, which may be controlled by the level andduration of the clutch commands. Therefore, for example, if theend-of-fill point occurs late, or after the desired end-of-fill region,the solenoid control valve can be commanded in a manner enabling fluidto fill the clutch 83 sooner thereby controlling the end-of-fill pointto occur sooner.

In the preferred embodiment, the end-of-fill point is compared with thedesired end-of-fill region. In one embodiment, the end-of-fill point maybe determined to have occurred before, during, or after the desiredend-of-fill region. In the preferred embodiment, the end-of fill pointmay be determined to have occurred in the fill ramp time,pre-desired-end-of-fill hold time, desired end-of-fill region,post-end-of-fill hold time, and modulation ramp region, as illustratedin FIG. 5.

Once the comparison is made between the end-of-fill point and thedesired end-of-fill region, a determination is made regarding whetherone or more of the clutch command parameters need adjusting to enablethe end-of-fill point to occur within the desired end-of-fill region.The appropriate parameters are then adjusted if need be.

In the preferred embodiment, no adjustments are made to the clutch fillcommand parameters if the end-of-fill point falls within the desiredend-of-fill region. In addition, no adjustments are made if theend-of-fill point occurs outside the five command pulse regions (fillramp region through modulation ramp region). If the end-of-fill pointoccurs outside these regions then the assumption is that the measuredend-of-fill point was not valid. In addition, no adjustment is made ifthe end-of-fill point occurs on the opposite side of the desiredend-of-fill region from a filtered end-of-fill point. The filteredend-of-fill point may be the averaged value of prior end-of-fill points,e.g., the last five end-of-fill points. In an alternative embodiment,the filtered end-of-fill point may be the last valid end-of-fill pointmeasured.

In the preferred embodiment, if an adjustment is necessary, e.g., theend-of-fill point occurred outside the desired region, the current levelof the clutch fill command is adjusted. However, the current level and,or the time duration of the clutch fill command may be adjusted.

If the end-of-fill point occurs late, i.e., after the desired region,then the clutch command parameters associated with the fill ramp time,hold time, or both may be increased. In one embodiment, if theend-of-fill point occurs in the post-desired-end-of-fill hold time, andthe filtered end-of-fill point is in either the desired region or thepost-desired-end-of-fill hold time, then the hold level, i.e., value ofthe current applied to the solenoid control valve during the hold timemay be increased. FIG. 6 illustrates one example of a prior andsubsequent command sequence 602 604 respectively. If the end-of-fillpoint occurs in the modulation ramp time, and the filtered end-of-fillpoint occurs in either the post desired-end-of-fill hold time or themodulation ramp time, then both the hold level, and fill ramp level maybe increased. FIG. 7 illustrates one example of a prior and subsequentcommand sequence 702 704 respectively.

The decision to modify the hold level, fill ramp level, or both isimplementation dependent. In addition, at what point the fill ramp levelis modified in addition to the hold level, if they are both modified, isalso implementation dependent. FIG. 6 and FIG. 7 illustrate oneembodiment of the adjustments that may be made in response to theend-of-fill point occurring after the desired end-of-fill region. Inaddition, FIG. 6 and FIG. 7 illustrated using the break between thepost-desired-end-of-fill region and the modulation time 706, todetermine whether to adjust the hold level, fill ramp level, or both. Amore aggressive approach to adjusting the location of the end-of-fillpoint may involve modifying the fill ramp level, along with the holdlevel, if the end-of-fill point occurs during thepost-desired-end-of-fill region and time line 708.

In the preferred embodiment, the initial values of the fill ramp leveland hold level are relatively low. The fill ramp and hold levels arethen adjusted according to the occurrence of the end-of-fill pointrelative to the desired region. The hold level may be adjusted primarilyto fine tune the timing of the end-of-fill point, and the fill ramplevel may be adjusted primarily to account for the end-of-fill pointoccurring in the extreme regions, such as the fill or modulation ramptime.

If the end-of-fill point occurs early, i.e., before the desired region,then either the fill ramp level, hold level, or both may be decreased.In one embodiment, if the end-of-fill point occurs in the pre desiredend-of-fill time and the filtered end-of-fill point occurred withineither the desired region, or pre desired end-of-fill time, then thehold level may be decreased. If the end-of-fill point occurs in the fillramp time, and the filtered end-of-fill occurs in the fill ramp time orthe pre desired end-of-fill time, then both the hold level, and thefirst ramp level may be decreased.

In one embodiment, once the appropriate clutch command parameter isidentified for adjusting, the amount of adjustment is determined.Predetermined adjustment values may be used. For example, a lookup tablemay be used that includes the fill ramp level adjustment value, holdlevel adjustment value, and the fill ramp and hold levels: upper limit,lower limit, and initial values. Therefore, each time an adjustment tothe hold level is needed, the hold level may be adjusted by thepredetermined hold level adjustment value, and then compared to an upperand lower limit to determine if the value has exceeded the limits. Ifthe value has exceeded the limits, then the hold level is set to thelimit. If the hold level exceeds the upper or lower limit, then, in oneembodiment, the ramp level may be adjusted also to account for the holdlevel limit being reached.

In an alternative embodiment, the adjustment to the hold or fill ramplevel may be dynamically determined based on how far outside the desiredregion the end-of-fill point occurred. Again, for small errors where theend-of-fill point occurred within the hold time, but outside the desiredregion, the hold level alone may be modified by a dynamically determinedvalue. In addition, if the end-of-fill time occurred in either the fillor modulation ramp regions, then both the hold and fill ramp level maybe dynamically modified to account for the error.

One embodiment of a method for controlling the end-of-fill point willnow be discussed with reference to FIG. 8, which depicts a flowchartrepresentative of the computer program instructions executed by theelectronic control module 40, shown in FIG. 1. As shown in FIG. 8, theprogram first initializes the fill ramp, hold, and modulation ramplevels <802>. The levels may be contained within a lookup table andaccessed during start up to initialize the levels. The program thendetermines whether a valid end-of-fill point has been detected <804>. Ifthe present end-of-fill point occurs outside of the region defined bythe fill ramp time through the modulation ramp time, then theend-of-fill point is determined to be invalid. In addition, if theend-of-fill point occurred on the opposite side of the desiredend-of-fill region, then the point is determined to be invalid. If thepoint is determined to be invalid, then the method loops back to thebeginning to wait for the next end-of-fill point.

In a third control block <806> the end-of-fill point is compared to adesired end-of-fill region. If the end-of-fill point falls within thedesired end-of-fill region, then no adjustment is needed to the clutchcommand parameters. The program then updates the filtered end-of-fillpoint based on the present end-of-fill point <808>. Control then returnsto the second control block <802> to determine if the next end-of-fillpoint is valid.

If the end-of-fill point falls outside the desired end-of-fill region,then a determination is made as to which clutch command parameters needadjusting <812>. For example, as described above, if the end-of-fillpoint falls within the modulation ramp time, then the fill ramp leveland the hold level may be increased for the next command sequence. Theappropriate clutch fill parameter(s) may be adjusted by either accessinga table of predetermined adjustment values, or by dynamicallydetermining the adjustment value based on the occurrence of theend-of-fill point relative to the desired end-of-fill region <814>.

Once the adjustment to the appropriate clutch fill parameter(s) is made,the adjusted value is checked to determine if it has exceeded an upperor lower limit <816>. Again, the upper and lower level limits may bepredetermined and stored in a table, or dynamically determined. If alimit has been exceeded then the level is set to the limit. In oneembodiment, if the level has exceeded the limit, then the level may beset to the limit, and the other level may be adjusted to compensate forthe overrun. For example, if the end-of-fill point occurs in the secondramp time, then the fill ramp level and hold level may be modified toadjust the end-of-fill point. If the fill ramp level, aftermodification, exceeds the upper limit, then the fill ramp level will belimited to the upper limit, and the hold level may be increased anadditional amount to compensate for not modifying the fill ramp level asmuch as desired.

Once the appropriate parameter(s) are adjusted, the end-of-fill point isused to update the filtered end-of-fill point <810>, and control returnsto control block <802>.

Industrial Applicability

The present invention discloses a system and a method for controllingthe timing of the filling of a fluid actuate. The system includes, afluid actuated clutch 83, an electronic controller adapted to detect anend-of-fill point for the fluid actuated clutch 83, compare theend-of-fill point with a desired end-of-fill point and adjust at leastone of a plurality of clutch fill parameters in response to thecomparison in order to control the timing of the filling of the clutch83, and a control valve that is activated by the electronic controller.

The present invention is advantageously applicable in controlling theshifting of a clutch 83 utilized in conjunction with a torque converter,typically, but not limited to, construction machines such as motorgraders, off-highway trucks, wheel loaders, bulldozers, and the like.The following description is only for the purposes of illustration andis not intended to limit the present invention as such. It will berecognizable, by those skilled in the art, that the present invention issuitable for a plurality of other applications.

In one embodiment, the end-of-fill point may be detected by detecting amarked decrease in the instantaneous value of the clutch slip as theend-of-fill point or end-of-fill time. This determination occurs whenthe instantaneous clutch slip is less than an reference value of theclutch slip. In one embodiment the reference clutch slip value is theaverage of a predetermined number of loops or cycles of clutch slip thatis divided by a predetermined factor. In an alternative embodiment, thereference clutch slip value is the output of a low pass digital filtersoftware algorithm, divided by a predetermined factor. The fill time isdefined as the time required to fill an on-coming clutch cavity withfluid. During this fill period, the clutch piston will stroke and theclutch plates touch-up. However, until the clutch plates are initiallycompressed, the clutch 83 cannot transmit any torque. Therefore, theend-of-fill time is important in order to ascertain when this criticalmoment is reached. The present invention can eliminate both earlyengagement and late engagement by adjusting the appropriate clutchcommand fill parameters in response to an early or late end-of-fillpoint. Early or late engagement can result in a torque spike that istransmitted through the drivetrain 10 of the machine and creates a“jerk”. The elimination of jerk will make the operator more comfortableand increase the life expectancy of the associated components locatedwithin the drivetrain of the machine. Elimination of late engagementpressure will prevent even greater amounts of jerk than earlyengagement.

In view of the foregoing, it is readily apparent that the subjectend-of-fill detection method, and dynamic adjustment of the end-of-fillpoint, provides a determination of end-of-fill in a very simple andeffective manner that results in a high quality engagement of a fluidactuated clutch.

Other aspects, objects and advantages of the present invention can beobtained from a study of the drawings, the disclosure and the appendedclaims.

What is claimed is:
 1. A system for controlling the timing of thefilling of a fluid actuated clutch comprising: a fluid actuated clutch;an electronic controller adapted to detect an end-of-fill point for saidfluid actuated clutch, compare said end-of-fill point with a desiredend-of-fill point and dynamically adjust at least one of a plurality ofclutch fill parameters in response to said comparison in order tocontrol the timing of the filling of the clutch; and a control valvethat is activated by said electronic controller and said control valveis operatively connected to said fluid actuated clutch.
 2. A system, asset forth in claim 1, further comprising: an input mechanism thatgenerates a signal, including a value for an input speed of said fluidactuated clutch and a value of output speed for said fluid actuatedclutch; and wherein said controller is further adapted to detect aninstantaneous clutch slip, which is a difference between said inputspeed of said fluid actuated clutch and said output speed of said fluidactuated clutch and detect when said instantaneous clutch slip is lessthan a dynamically determined reference clutch slip value, where thiscondition represents said end-of-fill point for said fluid actuatedclutch.
 3. A system, as set forth in claim 2, wherein said electroniccontroller is further adapted to responsively compare said end-of-fillpoint with a desired end-of-fill region, and adjust said at least one ofa plurality of clutch fill parameters in response to said end-of-fillpoint being outside said desired end-of-fill region, said parametersincluding a fill ramp command and a hold command, said fill ramp andhold commands having a current level and a time duration.
 4. The systemof claim 3, wherein said electronic controller is further adapted todetermine which of said plurality of clutch fill parameters to adjust inresponse to said comparison.
 5. The system of claim 4, wherein saidelectronic controller selects a predetermined adjustment value for saidparameter and responsively adjust said parameter.
 6. The system of claim4, wherein said electronic controller is adapted to dynamicallydetermine an adjustment value for said parameter.
 7. The system, as setforth in claim 1, wherein said controller is further adapted to comparesaid end-of-fill point with a previous end-of-fill point and adjust saidat least one of a plurality of clutch fill parameters in response tosaid end-of-fill point being outside said desired end-of-fill region,and said end-of-fill point being within a predetermined threshold ofsaid previous end-of-fill point.
 8. The system, as set forth in claim 7,wherein said previous end-of-fill point is a filtered end-of-fill point.9. The system, as set forth in claim 8, wherein said controller isadapted to adjust said hold command when said end-of-fill point occurslater than said desired end-of-fill region, and adjust said ramp commandand said hold command when said end-of-fill point occurs a thresholdvalue later than said desired end-of-fill region.
 10. The system, as setforth in claim 9, wherein said controller is adapted to adjust said holdcommand when said end-of-fill point occurred earlier than said desiredend-of-fill region, and adjust said hold command and said ramp commandwhen said end-of-fill point occurred a threshold value earlier than saiddesired end-of-fill region.
 11. A method for controlling the timing ofthe filling of a fluid actuated clutch, which is operatively connectedto a control valve that is activated by an electronic controller themethod comprising the steps of: determining an end-of-fill point;comparing said end-of-fill point with a desired end-of-fill point; anddynamically adjusting at least one of a plurality of clutch fillparameters in response to said comparison in order to control the timingof the filling of said fluid actuated clutch.
 12. A method, as set forthin claim 11, wherein the step of determining an end-of-fill pointfurther comprises the steps of: receiving a signal from an inputmechanism, including a value for an input speed of said fluid actuatedclutch and a value of output speed for said fluid actuated clutch;detecting an instantaneous clutch slip, which is a difference betweensaid input speed of said fluid actuated clutch and said output speed ofsaid fluid actuated clutch; and detecting when said instantaneous clutchslip is less than a dynamically determined reference clutch slip value,where this condition represents the end-of-fill point for said fluidactuated clutch.
 13. A method, as set forth in claim 12, furthercomprising the steps of: comparing the end-of-fill point with a desiredend-of-fill region; and adjusting said at least one of a plurality ofclutch fill parameters in response to said comparison, said parametersincluding a fill ramp command and a hold command, said fill ramp andhold commands having a current level and a time duration.
 14. The methodof claim 13, wherein the step of adjusting said at least one parameterfurther comprises the step of said adjusting at least one parameter whensaid end-of-fill point occurs outside said desired end-of-fill region.15. A method as set forth in claim 14, wherein the step of adjustingsaid clutch parameters includes the step of adjusting said parameters bya predetermined amount.
 16. A method, as set forth in claim 14, whereinthe step of adjusting said clutch parameters includes the step ofadjusting said parameters by a dynamically determined amount.
 17. Amethod, as set forth in claim 16, further comprising the steps of:comparing said end-of-fill point with a previous end-of-fill point andadjusting said at least one of a plurality of clutch fill parameters inresponse to said end-of-fill point being outside said desiredend-of-fill region and said end-of-fill point being within apredetermined threshold of said previous end-of-fill point.
 18. Thesystem, as set forth in claim 17, wherein said previous end-of-fillpoint is a filtered end-of-fill point.
 19. The system, as set forth inclaim 18, wherein the step of adjusting said at least one of saidparameters further comprises the steps of: adjusting said hold commandwhen said end-of-fill point is occurs later than said desiredend-of-fill region; and adjusting said ramp command and said holdcommand when said end-of-fill point occurs a threshold value later thansaid desired end-of-fill region.
 20. The system, as set forth in claim19, wherein the step of adjusting at least one of said parametersfurther comprises the steps of: adjusting said hold command when saidend-of-fill point occurs earlier than said desired end-of-fill region;and adjusting said hold command and said ramp command when saidend-of-fill point occurs a threshold value earlier than said desiredend-of-fill region.